Synergistic herbicidal mixtures



United States Patent 3,385 690 SYNERGISTEC HERBlQiDAL REEXTUREES RaymondW. Lnckcnbaugh, Wilmington, DeL, assignor to E. I. du Pont de Nemoursand Company, Wilmington, DeL, a corporation of Deiaware No Drawing.Continnationdn-part of application Ser. No. 415,484, Dec. 2, 1964, whichis a continuation-in-part of application Ser. No. 322,074, Nov. 7, 1963.This application Mar. 13, 1967, Ser. No. 622,450

16 Ciaims. (Cl. 71-93) ABSTRACT OF THE DISCLOSURE Synergistic herbicidalmixtures containing siduron, 1-(2-methylcyclohexyl)-3-phenylurea and oneof the following compounds:

. Diuron, 3- 3 ,4-dichlorophenyl) -1,1-dimethy1urea,

Linuron, 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea,

Neburon, 1-n-butyl-3 (3,4 dichlorophenyl) 1 -methylurea,

Diphenamide, N,N-dimethyl-2,Z-diphenylacetamide,

Norea, 3-(hexahydr0-4,7-methanoindan-S-yl)-l,1-dimethylurea,

Cotoran, 3-(m trifiuoromethylphenyl) 1,1 dimethyL urea and prometryne,2-methylmercapto-4,6 bis (isopropylamino -s-triazine.

Prior applications This application is a continuation-in-part of my US.application Ser. No. 415,484 filed on Dec. 2, 1964 (US. Patent3,309,192) which is a continuation-in-part of my US. applications Ser.Nos. 272,865 and 272,834 both filed Apr. 15, 1963 (nOW abandoned) whichare continuationin-part applications of my US. applications Ser. Nos;221,299 and 221,331 both filed Sept. 4, 1962 (now abandoned) which arecontinuation-in-part applications of my US. application Ser. No. 188,981filed Apr. 20, 1962 (now abandoned). It is also a continuation-in-partof my US. application Ser. No. 322,074 filed Nov. 7, 1963 (nowabandoned).

Background of the invention The ability of two compounds to createresults that are better than the additive efiect of the two compoundshas been a subject of avid study among scientists, especially in the artof herbicides. It is generally accepted that obtainingbetter-than-additive effect from a combination of compounds cannot bereliably predicted. Continued study has uncovered many individualcombinations that produce better than additive or synergistic results asit is usually called. The invention disclosed below adds anotherdisclosure to the study of synergism.

Summary of the invention This invention relates to methods andcompositions for destroying weeds. More specifically, it refers tomethods and mixtures for selectively controlling weeds by applying aherbicidal amount of a mixture of 1-(2-methylcyclohexyl)-3-phenylureaand another compound to areas of weed growth.

Description of the embodiments of the invention I have discovered thatby mixing a first compound, l-(2-methylcyclohexyl)-3-phenylurea, knowngenerically as siduron, with any one of a second compound at the belowindicated ratios and applying the resulting mixtures at herbicidal ratesto areas of weed growth the weeds are controlled. This control of weedsis achieved with rates of active compounds below that expected for thePatented May 28, 1968 individual compounds added together. The secondarycompound can be any one of the following.

Generic name: Chemical name Diuron 3-(3,4 dichlorophenyl) 1,1-

dimethylurea.

Linuron 3-(3,4-dichlorophenyl)-1 methoxy-l-methylurea.

Neburon l-n butyl 3 (3,4 dichlorophenyl)-1-methylurea.

Diphenamide N,N-dimethy1 2,2 dipheny1 acetamide.

Norea 3-(hexahydro-4,7 methanoindan-5-yl)1,l dimethylurea. 3 (mtrifluoromethylphenyl)-1,l-dimethylurea Not available Prometryne 2methylmercapto 4,6 bis- (isopropylamine) s triazine.

In the following discussion of the invention the compounds will bedescribed by their generic names for the sake of simplicity.

Use

Common name: Gramineae Smooth crabgrass Digitaria ischaemum. Largecrabgrass Digitaria sanguinalis. Annual brome Bromus brizacformis. Downybrome or cheat Bromus tectorum. Smilograss Orizopsis miliacea.Gooseg-rass Eleusine indica. Medusahead wildrye Elmyus caput-medusae.Colorado grass Panicum texanum. Switch grass Panicum vigratum. Dallisgrass Paspalum dilatatum. Bahia grass Paspalum notatum. PearlmilletPennisetum glaucum. Johnson grass Sorghum halepense.

Sorghum alumum. Sudan grass Sorghum sudanense. Barnyard grass Echinochloa crusgalli. Green foxtail Setaria viridis. Giant foxtail Setariafaberii. Yellow foxtail Setaria glauca. Fall panicum Panicumdichotomiflorum. Nimblewill M uhlenbergia schreiberi.

The following representative list sets forth broadleaved weed plantscontrolled by the mixtures used in this invention.

Common name: Gramineae Pigweed Amaranthus spp. Ragweed Ambrosia spp.Lambsquarters Chenopodium album. Pennsylvania Polygonum smartweedpensylvanicum. Purslane Portulaca oleracea. Horse purslane Trianthemaportulacastrum.

An annual plant is defined in the Journal of the Weed Society ofAmerica, vol. 10, #3, July 1962, as any plant that completes its lifecycle from seed in one year.

For the purposes of this specification, the plants of the above listincluding the annual Weed grasses and perennial weed grasses growingfrom seed such as Bermuda grass, nimblewill and Johnson grass are statedgenerically to be seedling weed grasses.

Weeds are defined as any unwanted plant. For the purposes of thisspecification it is assumed that annual grasses that are commonlycultivated such as ryegrass, wheat, barley and oats are not weeds.

The mixtures of this invention have utility for both preandpost-emergence control of an unusually large variety of weed species incrop and non-crop areas.

Process The preparation of the active toxicants used in the mixtures ofthis invention are taught by the following references:

Siduron, U.S. Patent 3,309,192,

Diuron, U.S. Patent 2,655,445,

Linuron, U.S. Patent 2,960,534,

Neburon, U.S. Patent 2,655, 444,

Diphenamide, Journal of Organic Chemistry, vol. 17, pp. 770-777 (1952),

Norea, U.S. Patent 3,304,167,

3 (rn-trifluoromethylphenyl)-l,l-dimethylurea, U.S. Patent, 3,134,665,

Prometryne, U.S. Patent 2,909,420.

The above references are herein incorporated by reference.

Compositions Compositions of this invention comprise a mixture used inthis invention together with one or more surfaceactive agents.

The surface-active agent used in this invention can be a wetting,dispersing or an emulsifying agent which will assist dispersion of themixture. The surface-active agent or surfactant can include suchanionic, cationic and nonionic agents as have heretofore been generallyemployed in plant control compositions of similar type. Suitablesurface-active agents are set out, for example, in Searle, U.S. Patent2,426,417; Todd, U.S. Patent 2,655,447; Jones, U.S. Patent 2,412,510; orLenher, U.S. Patent 2,139,276. A detailed list of such 'agents is setforth in Detergents and Emulsifiers Annual (1964), by John W.McCutcheon, Inc.

Suitable surface-active agents for use in compositions of the presentinvention are: polyethylene glycol fatty acid esters and fatty alkylolamide condensates, alkylaryl sulfonates, fatty alcohol sulfates, dialkylesters of sodium sulfosuccinate, fatty acid esters of sodiumisethionate, polyoxyethylene ethers and thioethers and long chainquaternary ammonium chloride compounds.

Surface-active dispersing agents such as sodium lignin sulfonates, lowviscosity methyl cellulose, polymerized sodium salts of alkylnaphthalenesulfonic acids are also suitable in the herbicidal compositions of thisinvention.

Among the more preferred surfactants are the anionic and non-ionic type.Among the anionic surface-active agents, preferred ones are alkali metalor amine salts of alkylbenzene sulfonic acids such as dodecylbenzenesulfonic acid, sodium lauryl sulfate, alkylnaphthalene sulfonates,sodium N methyl-N-oleoyltaurate, oleic acid ester of sodium isethionate,dioctyl sodium sulfosuccinate, sodium dodecyldiphenyloxide disulfonate.Among the non-ionic compounds, preferred members are alkyl phenoxy poly(ethyleneoxy)ethanols such as nonylphenyl 'adducts with ethylene oxide;trimethylnonyl polyethylene glycol ethers, polyethylene oxide adducts offatty and rosin acids, long chain alkyl mercaptan adducts with ethyleneoxide and polyethylene oxide adducts with sorbitan fatty acid esters.

In general, less than 10% by weight of the surfaceactive agents will beused in compositions of this invention and ordinarily the amount ofsurface-active agents will range from 15% but may even be less than 1%by weight.

Additional surface-active agents can be added to the above formulationto increase the ratio of surface-active agent:active agent up to as highat 5:1 by weight. Normally the purpose of adding higher amounts ofsurfactant is to increase the growth retardant effect of the mixture.When used at higher rates it is preferred that the surfactant be presentin the range of one fifth to five parts surfactant for each one part ofits active toxicants.

Plant growth retardant compositions of this invention can contain, inaddition to a surfactant, finely divided inert diluents such as talcs,natural clays including attapulgite clay and kaolinite clay,pyrophyllite, di'atomaceous earths, synthetic fine silicas, calciumsilicate, carbonates, calcium phosphates, sulfur, lime and such floursas walnut shell, wheat, redwood, soybean and cottonseed.

Preferred diluents are clays of hydrated aluminum silicate, hydratedaluminum magnesium silicate and hydrated aluminum magnesium ironsilicate.

The amount of the finely divided inert solid diluent can vary widely butwill generally range from 10 to 98% by weight of the growth retardantcomposition. The particle size can vary considerably but will ordinarilybe somewhat under 50 microns in the finished formulation. Suchcompositions are prepared by blending the ingredients and grinding in ahammer mill or an air attrition mill or similar device until uniformpowders are obtained which have a particle size smaller than 50 microns.Compositions containing a surface-active agent 'and a solid inertdiluent are preferably wettable powders containing from 25 to 50% of themixture of active toxicants.

The mixtures of this invention can also be formulated as high strengthcompositions in which the active ingredient may be present in amountsranging from 99%. The remainder of the composition comprisessurface-active agents, preferably in amounts of from 0.2 to 2% anddiluents, as described above. Such compositions are prepared by blendingand grinding the ingredients to obtain a homogeneous powder of fineparticle size.

Compositions of these plant growth retardants and inert solid diluentcan also be formulated into granules and pellets. In such compositions,the diluent will generally range from 65 to 99% and the activeingredient can range from 1 to 35%. It should be understood that it willnot be necessary to include a surfactant in the granular and pelletizedcomposition. To prepare granules the herbicides can be dissolved in asolvent, and this solution can be sprayed over pre-formed clay granules,expanded verciculite or the like while agitating the mixture todistribute the active ingredient over and throughout the granular mass.Such granules can range in particle size of from +60 mesh to +4 mesh,and an active ingredient content of 1 to 6% is preferred. It is alsopossible to make such granules by mixing the finely divided diluent andfinely divided herbicide, for instance by grinding together, and thenforming granules by adding water, tumbling and drying the resultingspheres.

Pellets can be prepared by extruding a mixture that comprises themixture of active toxicants, pelleting clay diluent and water intostrands, cutting these, and drying the product. Pellet size can rangefrom 10 mesh to larger shapes such as inch cubes. Pellets preferablycontain from 5 to 35% of the active toxicants. In addition to thediluents, pelletized and granular compositions can contain additivessuch as binders, surfactants and the like.

In addition to the formulation described above, suspension concentratescan also be prepared. These formulations are prepared by Wet milling theingredients; i.e., ball milling or by sand grinding using the methoddescribed in Hochberg, U.S. Patent 2,581,414, issued Aug. 19, 1948, orLittler, US. Patent 3,060,084 issued Oct. 23, 1962. Using the methodsdescribed in these patents, fine particles of the active compoundswithin the scope of this invention will be dispersed evenly in adiluent. Such compositions normally contain from to 50% activeingredient and are characterized by having particles which aresubstantially less than 5-20 microns in diameter.

Water extendable oil compositions can also be employed with one or moreof the mixtures of this invention. In these plant growth regulantcompositions, surfaceactive agents and an oil form a liquid which can beconveniently poured and measured. Such solutions can be mixed with waterat the point of application to form an emulsion containing the herbicideand the surface-active agent. Such compositions have the advantage thatthe oil will often act as a foam inhibitor and thus reduce the tendencyfor large amounts of surfactants to form objectionable foam. These oilformulations can be either dispersions of the active toxicants in finelydivided form in non-solvent carriers, or they can be solutions insolvent carriers. A non-solvent carrier is an oil in which the urea haslow solubility, for instance less than 0.1% at C. Many aliphatichydrocarbons are examples of such nonsolvent carriers. Solvent carriersinclude toluene, kerosene, xylene, alkylated naphthalenes, DMF,N-methylpyrrolidone, cyclohexanone, isophorone and the like. Preferably,the oils should be water immiscible and be of a type in which the activeagent will be soluble in the amounts used in particular formations. Thedispersions are prepared by Wet-milling the ingredients, for example, ina ball mill or sand mill. The solutions are prepared by blending andagitating the ingredients, possibly with application of heat.

In these emulsifiable oil concentrates, the mixture of active toxicantswill be present in amounts ranging from 5 to by weight. Preciseconcentrations of active toxicants, of course, will depend on theintended use of the composition. When mixed with water at the point ofapplication the oil concentrate will be diluted so that in the finalformulation the active toxicants will be present in amounts ranging from0.5% to 2% by weight. it will be understood that foliage application ofthe emulsifiable compositions will have utility for regulating thegrowth of several undesirable annual grass species and broad leafspecies along highway and railroad rights-of-way, as well as otherlocations.

It is, of course, also possible to use such oil compositions of theactive toxicants by extending them with other oils, for example, dieseloil, herbicidal oil, and the like for uses such as weed control onrailroad rights-of-way.

The percent ranges set forth above are all based on the weight of theindicated ingredients.

Application The mixtures of this invention are applied directly to thesoil as pre-emergence or as post-emergence treatments or to weed plantsfoliage as a post-emergence treatment. They also can be mixed intimatelywith the soil in preemergence treatments. Rates of application of thesiduron in the mixture can be in the range of /2 to 20 pounds per acreand will preferably be used as the rate of 1 to 8 pounds per acre tocontrol the seedling weed grasses described above. Rates of siduron ashigh as 24 pounds have been used in tests on established turf grasseswithout undesirable injury.

More specifically, as a pre-emergence application on crop lands, 2 to 8pounds per acre of siduron used in this invention will control thegrowth of weed grasses. There is a good safety margin to crop plantssuch as cucumbers, cotton, potatoes, flax, squash, lima beans, corn,eggplants, red clover, ryegrass, tomatoes, lespedeza, peppers, soybeans,red beets, alfalfa, sugar beets, green beans, carrots, peanuts, okra andthe like. The weed grass usually emerges and then fails to develop,showing symptoms of severe growth retardation. The siduron used in theinvention retards a weed grass such as crabgrass without harmingcultivated annual grasses such as ryegrass.

As an application on established growing lawns before a weed grass suchas crabgrass appears, growth of crabgrass is controlled with 2 to 16pounds of siduron per acre. There is no injury to established Kentuckybluegrass, bentgrass, creeping red fescue or common Bermuda grassgrowing from rhizomes. The crabgrass emerges and then fails to develop.

As a directed post-emergence application on crop lands at any time fromthe moment the weeds emerge to the three leaf stage, 2 to 8 pounds peracre of siduron will prevent the further development of the weed grass.There is'no percptible injury to crop plants such as cucumbers, cotton,potatoes, flax, squash, lima beans, eggplant, red clover, tomatoes,lespedeza, peppers, soybeans, red beets, alfalfa, sugar beets, greenbeans, carrots, peanuts, okra, corn and the like.

As an application on established lawns after the crabgrass emerges tothe 3 leaf stage, 3 to 16 pounds per acre of siduron ingredient willprevent the further development of crabgrass without injury to theestablished lawn grasses.

The mixtures of this invention can be applied admixed with otherchemicals which are used in agronomic and horticultural management andare compatible with the compounds of this invention. Such chemicals maybe, but are not restricted to, the classes of chemicals commonly knownas plant nutrients, fertilizers, insecticides, fungicides, andnematocidcs. Typical of the insecticides that can be used are:

1,2,3,4,10,10-hexachloro 6,7-epoxy 1,4,40c,5,6,7,8,8ot octahydro1,4,5,S-dimethanonaphthalene (Dieldrin) 1-2 pounds per acre1,2,4,5,6,7,8,8-octachloro 4,7methano 3u,4,7,7a-tetrahydroindane(Chlordane), 25-10 pounds per acre 1,1,1-trichloro2,2-bis(p-methoxyphenyl)ethane (Methoxychlor), 2-4 pounds per acre1,1,l-trichloro 2,2-bis(p-chlorophenyl)ethane (DDT),

10-20 pounds per acre, and

1-naphthyl-N-methylcarbamate (Sevin) 2-4 pounds per acre.

Insecticides in compositions of this invention are present at the rateof 0.1 to 10 parts by weight for each one part by weight of the mixtureof active toxicants.

Fungicides that can be used in conjunction with the active toxicants ofthis invention include:

etal salts of ethylene bisdithiocarbamic acid, e.g. sodium, manganese,zinc and iron salts; N-trichloromethyl-mercapto4-cyclohexene-1,2'dicarboximide; Phenylmercury acetate; Inorganicmercury salts; Methylmercury dihydroxypropyl mercaptide; Methylmercuryacetate; N-trichloromethylthiophthalimide;2,3-dichloro-,1,4-naphthoquinone; 2,3,5,6-tetrachloro-l,4-benzoquinone;2,4-dichloro-6-(o-chloroanilino)-s-triazine; Copper A; Metal salts ofalkyl and dialkyl dithiocarbamic acid, e.g.

Zn, Na, K, Fe, Mn, Ni; Zinc pyridinethione; S-( l-oxido-2-pyridyl)-isothiuronium chloride; Tetrachloroisophthalonitrile;Tetramethylthiuram disulfide; Hydroxymercurichlorophenol and mixtures ofthese last two, and methyl mercury dicyandiamide.

When present in compositions of this invention the above-describedfungicides will be present at the rate of .02 to 10 parts by weightbased on the weight of the two active toxicants present in thecomposition.

The control of Weed grasses with 1-(2-methylcyclohexyl)-3-phenylurea isadvantageously accomplished together with the use of conventionalherbicides in situations where crabgrass is growing with weedscontrolled by the second herbicide. The synergistic effect achieved bycombining the several conventional herbicides mentioned above withsiduron allows for a substantial saving of chemicals and expenditure bythe farmer.

Illustrative of herbicides and their herbicidal amount that can be usedin conjunction with siduron in sprays and granular formulations to takeweeds out of desirable plants are the following:

The amount of second herbicide set forth in the left column is inaddition to a base rate of two pounds per acre of siduron. Aherbicidally effective amount of siduron will range from 1 to 8lbs/acre. Accordingly the amount of second herbicide in the mixture willbe more or less than that described above depending on the quantity ofsiduron in the mixture. A herbicidally effective amount of the mixturewill vary from a mixture containing one pound of siduron and 0.1 poundof second herbicide up to eight pounds of siduron and as much as sixteenpounds of second herbicide.

Fertilizers commonly called plant nutrients can also be applied togetherwith the mixture used in this invcntion. The plant nutrients include thecommonly used compounds of nitrogen, phosphorus, and potassium; i.e.ammonium sulfate, ammonium nitrate, urea, methylene ureas, low molecularweight urea-formaldehyde polymers, sodium nitrate, anhydrous ammonia,aqueous ammoniacal solutions of urea, or ammonium nitrate, aqueoussolutions of urea, or ammonium nitrate, ammonium phosphates,superphosphates, triple superphosphates and phosphoric acid and thepotassium salts such as the chloride, sulfate and nitrate. The plantnutrients are applied individually or in a mixture with each other asso-called complete mixtures of N-P-K which may also contain one or moreof the trace element plant nutrients; i.e., manganese, zinc, iron,boron, magnesium, etc.

The active toxicants are preferably added to such fertilizer mixtures orcompounds following the usual mixing, granulation, ammoniation, dryingor other manufacturing operations to avoid possible adverse effects ofsuch operations on the efiicacy of the' compounds as weed grassretardants or for controlling annual broadleaf weeds.

It is understood that the mixtures of this invention are applied to thelocus of the grass or broadleaf weeds growth. By locus is meant theplant itself when visible above the ground and when the plant is notvisible the immediate area of soil where the broadleaf or grass weedplant is developing.

The following additional examples, in which all percents unlessotherwise specified are by weight, are provided so as to more clearlyexplain this invention.

8 Example 1 Percent Siduron 40 Norea 10 Diatomaceous silica 48 Coconutacid ester of sodium isethionate 1 Sodium lauryl sulfate 1 Theingredients are blended and micropulverized to pass a 60 mesh screen.

This wettable powder formulation in the amount of 2.5 pounds of activetoxicants is added to gallons of water in a spray tank. A surfactantsuch as trimethylnonyl polyethylene glycol ether is added to thismixture at the rate of 6 pounds. This tank spray mixture is applied toone acre of cotton which is infested with crabgrass in the 1 to 2 leafstage and several species of broadlcaf weeds Excellent retardation ofthe weeds is obtained. The cotton grows free of most weed competition.

The above ingredients are blended and micropulverized to achieve aparticle diameter of less than 50 microns.

This wettable powder formulation in the amount of 2.5 pounds of activetoxicants is added to 80 gallons of water in a spray tank. Six pounds oftrimethylnonyl polyethylene glycol ether is added to this mixture. Thistank spray mixture is applied to one acre of cotton prior to emergenceof weed plants. Weeds in the area include Digitaria spp., Selaria spp.,Amaranthus spp., and Chenopodium album. The weeds are effectivelycontrolled by the mixture and a good crop of cotton is obtained.

Example 3 The following wettable powder can be diluted with water or itmay be made up as a tank mix in conjunction with 0.2-5 parts oftrimethylnonyl polyethylene glycol ether per part of active ingredient:

Percent Siduron 62.3 Diuron 7.7 Attapulgite clay 18.0 Dioctyl sodiumsulfosuccinate 2.5 Na HPO 2.5 Partially desulfonated sodium ligninsulfonate 2.0 Synthetic fine silica 5.0

This wettable powder formulation is applied at the rate of 2.25 poundsactive toxicants per acre in conjunction with 4 pounds of sulfactant in40 gallons of water per acre as a directed post-emergence spray tocrabgrass in the 1 to 3 leaf stage and several broadleaf species ofweeds in a field of cotton when the cotton is 6 inches high. Excellentcontrol of the crabgrass and broadleaf weeds is obtained.

Example 4 The same formulation and procedure of Example 3 s used, butthere is substituted an identical amount by weight of linuron for thediuron. The composition is applied at the same rate to a field ofsoybeans. Crabgrass, foxtail, pigweed, and several other weed speciesare present in an early development stage. Excellent control of theweeds is obtained. The soybeans show normal growth.

Example 5 The same formulation and procedure of Example 3 is used, butthere is substituted an identical amount by weight of prometryne for thediuron. The composition is applied at the same rate to a similar fieldof cotton.

9 Weeds are effectively controlled. The cotton shows normal growth.

Example 6.Pellet formulation The following pellet formulation isprepared:

Percent Siduron 5.5 Diphenamid 5.5 Anhydrous sodium sulfate 10.6Mississippi sub-'bentonite 33.0 Kaolin Clay 33.0 Lignin sodium sulfonate13.0

These ingredients are mixed and blended by micropulverizing.Approximately 18% water as calculated on a weight basis is added to theformulation and thoroughly mixed. The resulting product is extruded intopellets through a screw type extrude'r fitted with a die containingorifices of %2 inch. The extruded strands are conveniently cut intosmall pellets as they come out of the extruder die. The pellets are airdried. After drying the pellets can be easily handled and applied assuch. However, they readily soften and disintegrate when mildly agitatedin water and can also be applied in water rather than as the pellets.

The pellets are applied at the rate of two pounds of active toxicants toa one acre field of peanuts. P-igweed and Johnson grass weeds areeffectively controlled. The peanut crop shows normal growth.

Example 7 Percent Siduron 52.5 Neburon 17.5 Sodium alkyl naphthalenesulfonate 2.5 Partially disulfona-ted sodium lignin sulfionate 3.0

Kaolin Clay 24.5

The above ingredients are blended and micropulverized to a particle sizeless than 50 microns in diameter.

The formulation described above is applied preemergence at the rate of 8pounds of active tox icants per acre in 100 gallons of water for thecontrol of crabgrass growth in an established bluegrass-fescue lawn.Excellent retardation of cra'bgrass is obtained, without noticeabledamage to the desirable turf grasses.

In order to establish synergism between siduron and the other activetoxicants in the mixtures of this invention, tests were carried outusing the sidunon-diuron mixture. Calculation of synergism was based onthe methods of Dr. S. R. Colby as described in Weeds, vol. 15, No. 1,pp. 20-22 (January 1967).

Diuron and siduron were compared separately and together upon applyingcompositions containing the toxicants to areas in which pigweed andJohnson grass were growing. A tabulation of the test results follows.

I. A synergistic herbicidally effective amount of a mixture comprisingone part by weight of I-(Z-methylcyclohexyl)-3-phenylurea and 0.1 to 2parts by weight of a second compound selected from the group consistingof:

3- (3,4dichlorophenyl) -1,1-dirnethylurea.

3-(3,4-dichlorophenyl)-1-methoxy-l-methylurea,

l-nbutyl-3-(3,4-dichlorophenyl)-1-methylurea,

N,N-dimethyl-Z,Z-diphenylacetamide,

3-(hexahydro-4,7-methan0indan5-yl)-l,l-

dimethylurea,

3-(m-trifluoromethylphenyl) -1,1-dimethylurea,

2-methylmercapto-4,6-bis- (isopropylamino) -striazine.

2. A synergistic herbicidal mixture according to claim 1 wherein thesecond compound is 3-(3,4-dichlorophenyl)-1,1-dimethylurea.

3. A synergistic herbicidal mixture according to claim 1 wherein thesecond compound is 3-(3,4-dichlorophen yl) -1methoxy-1-methylurea.

4. A synergistic herbicidal mixture according to claim 1 wherein thesecond compound is 1-nbutyl-3-(3,4-dichlorophenyl) -1-methylurea.

5. A synergistic herbicidal mixture according to claim 1 wherein thesecond compound is N,N-dimethyl-2,2-diphenylacetarnide.

6. A synergistic herbicidal mixture according to claim 1 wherein thesecond compound is 3-(heXahydro-4,7-methanoindan-S-yl)-1,1-dimethylurea.

7. A synergistic herbicidal mixture according to claim 1 wherein thesecond compound is 3-(m-trifluoromethy1- phenyl)-1,1-dimethy-lurea.

8. A synergistic herbicidal mixture according to claim 1 wherein thesecond compound is 2-methylmercapto-4,6- bis-(isopropylamino-s-triazine.

9. Method of destroying weeds comprising applying to the locus to beprotected a herbicidally effective amount of a mixture of one part byweight of 1-(2-methylcyclohexyl)-3-phenylurea and 0.1 to 2 parts byweight of a second compound selected from the group consisting of:

3 3,4-dichlorophenyl) -1,1-dimethy-lurea,

3- 3 ,4-dichlorophenyl) l-methoxy- 1 -methylurea,

1-n-butyl-3- (3 ,4-dichloropheny1) -1-methylurea,

N,N-dimethyl-2,2-diphenylacetarnide,

3-(hexahydro-4,7-methanoindan-S-yl)-1,1-dimethylurea,3-(m-trifluoromethylphenyl)-1,1-dimethylurea,

Z-methylmercapto-4,6-bis-(isop-ropylamino)-s-tri-azine.

10. Method according to claim 9 wherein the second compound is3-(3,4-dichlorophenyl)-1,1-dimethylurea.

11. Method according to claim 9 wherein the second compound is3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea.

12. Method according to claim 9 wherein the second compound is1-n-butyl-3-(3,4-dichlorophenyl)-1-methylurea.

13. Method according to claim 9 wherein the second compound isN,N-dimethyl-2,Z-diphenylacetamide.

14. Method according to claim 9 wherein the second compound is3-(hexahydro-4,7-methanoindan-5-yl)-1,1- dimethylurea.

15. Method according to claim 9 wherein the second compound is3-(m-trifluoromethylphenyl)-1,1-dimethylurea.

16. Method according to claim 9 wherein the second compound is2-methylmercapto-4,6-bis- (isopropylamino JAMES C). THOMAS In, PrimaryExaminer.

